Synthesis gas, or syngas, is made up of hydrogen (H2) and carbon monoxide (CO) and may contain some carbon dioxide (CO2) (and may contain other components as well). Syngas is available from a variety of sources, such as reforming natural gas, coal-bed gas or naphtha, from the gasification of coal, biomass, carbon rich materials, municipal wastes, etc. Using the well-known Fischer-Tropsch process, the syngas is passed over a catalyst and converted to hydrocarbons. When used to produce mixed alcohols, the process is a modified Fischer-Tropsch process and is generally referred to as Mixed Alcohol Synthesis (MAS). Stevens, U.S. Pat. Nos. 4,752,622, 4,752,623 and 4,831,060 disclose MAS catalysts and processes.
Mixed alcohols range from methanol (C1—OH), ethanol (C2—OH), propanol (C3—OH) on up. Alcohols of C3, C4, etc. are referred to as higher alcohols. In general, higher alcohols are preferred for their higher BTU content over the lower alcohols of C1 and C2. In addition to the higher BTU content, higher alcohols have a lower volatility due to their longer molecules.
On its face, the Stevens '622 patent seems promising in disclosing yields of higher alcohols. However, in practice, these results have not been replicated despite numerous attempts. It is desired to produce greater yields of the higher alcohols from the Fischer-Tropsch process in a repeatable manner. There are however reproducible data from Stevens '622 patent catalyst formula producing alcohols comprising 28-53 percent by weight methanol, 39-47% weight ethanol, 6-14% weight propanol, 0.7-3% weight butanol, and 0-2% weight pentanol.
We have found that using vanadium in the catalyst increases the yield of higher alcohols in a repeatable manner. In the prior art, it is known to use the Fischer-Tropsch process to make hydrocarbons, Miller, U.S. Pat. No. 4,840,931. The catalyst has a transition metal taken from the group of cobalt, molybdenum and vanadium. The metals are oxides.
In Quarderer, U.S. Pat. No. 4,825,013, the Fischer-Tropsch process is used to synthesize mixed alcohols, not hydrocarbons. The catalyst is on a support. While the support may contain vanadium, the catalyst does not.